100 EOCENE MOLLUSCA. 
oblique ; radiated or obsoletely costulated, finely decussated; margin toothed, area of 
connector rather narrow ; beaks depressed. 
Diameter, 2 inches. 
Localities. Stubbington (Zdwards). 
Belgium: Le calcaire d’ Afflighem et d’Audenarde, Kleyn Spauwen (WVys?). 
France: Grignon, Courtagnon (Deshayes). 
A large number of fossils from various localities and from various formations have 
been figured and described under the above name; Brongniart has given it to a species 
from the neighbourhood of Turin, and Dubois to one from Volhynia, but these are, perhaps, 
not strictly within what are called specific limitations. The principal character, as its — 
name imports, is a tumid or puffed-up appearance of the specimen, with a very slight 
deviation from the orbicular or rather circular form of the margins. There is also a 
slight angularity on the siphonal region, as is often the case in shells of this genus. The 
dental area is curved and well furnished with teeth, and the area for connexus is rather 
small, but it increases considerably as the shell enlarges, and it is comparatively wider in 
the old shell, where the ligamental portion of the connector has obliterated or overlapped 
the denticles in the centre of the hinge area. The surface of the English specimens is 
seldom or never in such a good state of preservation as those from the Paris basin, where 
the small interstices between the rays and the lines of growth may be distinctly seen, 
giving a slightly punctured appearance to the exterior, and in those shells a portion of the 
connector is often preserved. 
8. PecruncuLus quasipuLvinatus, 8S. Wood. Tab. XVI, fig. 1, a, 4. 
Spec. Char. P. testa lenticulato-complanatd, compressa, equilaterali, aquivalvi, sub- 
transversd ; radiato-striatd, striis depressis, obsoletis ; concentricé decussatd ; marginibus 
crenulatis ; ared connexitis perangustd ; umbonibus depressiusculis. 
Shell compressed or depressedly lenticular; equilateral, equivalve, rather transverse or 
elongated ; covered with depressed and obsolete striz ; decussated by obscure or irregular 
lines of growth ; margins crenulated ; area of connector narrow ; beaks depressed. - 
Diameter, 24th inches. 
Locality. Bracklesham. 
This has hitherto been placed in cabinets under the name of P. pulvinatus, var., but I 
think the differences are such as to entitle it to a separate specific position, and the speci- 
mens themselves appear to show a permanence of difference which give them as good a 
claim for isolation as most others in this perplexing genus. Our shell is much more com- 
pressed than the true pulvinatus, and the proportions in this are also different, the shell 
being more transverse or elongated. It differs also from the French shell called psewdo- 
pulvinatus, which is neither so compressed nor so transverse as our present species. I 
